So I am curious, can we refuse to pay the 18%? What if we didn’t feel that the service warranted 18% tip?
Unlike tips, the customer must pay service charges if they were made aware of the service charge prior to services being performed. Did the restaurant put a note anywhere in tiny print on the menu, or on a wall/front door, or mention it etc? If you don't pay the service charge and the restaurant can demonstrate this was mentioned somewhere (even if you didn't see it) you would be guilty of theft. Of course, taking you to court to collect this amount would be a waste of their time.
I would consider is it worth the hassle to not pay the service charge, maybe some chef with a knife would come after you or your car tires? What tip would you have left? So how much money are you really talking about? Note that tipping is always optional, even if they add a 20% gratuity for parties greater than 6. Service charges are never optional and is just a way for merchants to increase their income without increasing their prices. I remember going to a restaurant where the menu prices were cash only. They added a surcharge if you used credit cards - but this was mentioned in their menu.
Sounds like you should have just left when you found out about no credit cards or the charge for water. At least they charged you 18% on the pre-tax amount. I've seen cases where they charge on the after tax portion!
Check out their recent Yelp reviews. They charge 18% “Because people like you don’t tip” said the owner!